* |
Summary:The goal of this project is to enable the development of a scientific and technical infrastructure for the safe and efficient use of hydrogen as a fuel source. For example, figure 1 shows the influence of hydrogen on the ductility and fracture behavior of a steel that is relatively resistant to effects of hydrogen. We will provide the nation with reliable measurements, standards, and data for assessing the mechanical behavior of materials in hydrogen and conditions related to hydrogen production, transport, distribution, and use. Description: Impact and Customers Major Accomplishments:This project is part of the American Competitiveness Initiative proposed by the President in the 2006 State of the Union Address and approved by the US Congress in February 2007. This project requires close coordination and collaboration with DoE, ASME, DoT Office of Pipeline Safety, and industry. This collaboration is facilitated primarily through participation in the DoE Pipeline Working Group (PG). NIST staff began attending meetings and workshops held by these groups before this project started and will participate in these meetings for its duration. Once funding for this project was approved, NIST immediately began planning to bring these groups to NIST for a workshop on hydrogen testing discussed above. At the NIST workshop, representatives discussed materials, testing, and standard issues. At its conclusion, the DoE PG subgroup on testing methods met to coordinate test activities and plan round robin testing including NIST. This plan was reviewed by the entire PG and approved at their meeting the following month. The key assumption of this project is that once inside a metal, the same hydrogen concentration (activity) will have the same influence on mechanical properties regardless of the actual hydrogen source. Only the thermodynamics and kinetics of hydrogen absorption differ with the hydrogen source. Through the use of electrochemistry, it is theoretically possible to control hydrogen activity with potential and measure hydrogen absorption, or desorption, with current. Experimentally, passivating surface films, corrosion reactions, and hydrogen recombination can cause large deviations from theory. Therefore, the research in this program began with electrochemical absorption and desorption experiments to identify the ideal solutions, reference electrodes, and other conditions for studying hydrogen absorption, diffusion, trapping and embrittlement. Figure 2 is a schematic of the electrochemical cell used for these experiments. Prior to the start of this project, we worked with DoE’s Jefferson National Accelerator Facility on springback of deep-drawn Nb and demonstrated that hydrogen could explain the observed broad range of tensile and plastic flow behavior. To test the hypothesis that hydrogen absorbed during processing was responsible for these variations, samples were heat treated in vacuum and examined. The vacuum treatment lowered the yield stress, doubled the ductility, and reduced serrated yielding during plastic flow (the Portevin-Le Chatelier or PLC effect). Time series analysis techniques were used to evaluate the plastic flow curves, as shown in figures 3 and 4, and dynamic mechanical analysis was used to evaluate the influence of outgassing on the elastic and anelastic behavior. The results were presented at an international conference on large grain and single crystal Nb in Brazil and was published by AIP. |
Start Date:October 1, 2008End Date:on goingLead Organizational Unit:mmlCustomers/Contributors/Collaborators:Materials Reliability Division: J. D. McColskey, T. Siewert, A. Slifka, N. E. Nanninga, and Y. S. Levy DoE, Pipeline Working Group (SNL, ORNL, SRNL, ASME) DOT, Office of Pipeline Safety Pipeline Standards Developing Organization Coordination Council (AGA, API, ASME, ASTM, AWS, NACE, NFPA) Facilities/Tools Used:
Staff:Related Programs and Projects:Associated Products:Project Summary (PDF) Contact
General Information: 100 Bureau Drive, M/S 8553 |